The focus of the Animal Core Laboratory (ACL) is to provide immunodeficient and specific mutant mice for the Program Projects. Chimeric mouse human hybrids have become an important research tool for the evaluation of the reconstitution and differentiation potential of hematopoietic and immunologic progenitor populations. Genetically modified strains such as the adenosine deaminase null (ADA null) or GFP transgenic mouse strains are powerful tools in the evaluation of transplantation. The Animal Core Laboratory (Core C) will provide seven services for the projects in the grant: 1) Establishment and maintenance of breeding colonies of mutant mice, mainly immunodeficient, for the projects; 2) Genotyping of mice for either breeding or experimentation; 3) Provision of pups and adults for experiments; 4) Transplantation of immune deficient mice with human cells; 5) Establishment of strains of mice with congenic markers to facilitate monitoring of cells following administration of transplanted or transduced cells, or other strains required for the Program Projects; 6) Development and testing of new strains of immune deficient mice with superior engraftment of human grafts and normal life spans; 7) Health monitoring and day-to-day care of immunodeficient mice; and 8) Training of research personnel on the care and techniques used with of immunodeficient mice. The Core will be housed within the Animal Care Facility at Childrens Hospital Los Angeles and run under the direction of Dr. Carolyn Lutzko. In summary the ACL will provide valuable and efficient service for the projects by developing, testing, maintaining the colonies and providing the mice required for the Program Projects.